Stretching machine jaws



Jap- 3, 1953 E. w. COOPER STRETCHING MACHINE JAWS Original Filed March 11, 1944 INVENTOR. W. COOPER A TTOR/VEY Patented Jan. 13. 1953 STRETCHJNG MACHINE JAWS Ellis W. Cooper, Los- Angeles, Calif., assignor to North American Aviation,

Inc., Inglewood,

Calif., a corporation of Delaware Original application March 11, 1944, Serial No. 526,115. Divided and this application July 22, 1949, Serial No. 106,828

1 claim. (01. 153-35) This invention is a divisional application from application Serial No. 526,115, filed March 11, 1944, for Stretching Machine Jaws and Method of Making the Same and which issued as United States Patent No. 2,482,841 on September 27, 1949, and relates to the art of making jaws for stretching machines of the type adapted to stretch extruded structural members so as to increase their tensile strength and particularly to a novel stretching machine jaw so adapted. It has been discovered that by stretching structural members such as those used in forming the wing ribs of aircraft that a very considerable increase in tensile strength is obtained. The structural member may be given the proper airfoil shape in the stretching operation.

The lengths of structural material are attached to the stretching members of the press by means of jaws which grip the end portions of such structural members. Because of the extremely high tension loads imposed upon the structural members in the stretching operation, these jaws must be constructed so as to firmly grip a large portion of the cross-sectional area of each end portion of a structural member. It is found that if any considerable area is not engaged by the jaws, the corresponding portion of the structural member may not be stretched as much as those portions that are directly in the line of pull of the engaging portions of the jaws.

In order to secure adequate grip, the jaw facings must be formed with teeth. These teeth are formed by cross-grooving the facings. They must be extremely hard, and it is customary to employ tool steel, which is usually hardened. In the past it has been customary to machine each jaw from a single block of tool steel. The cost of producing in this manner a set of jaws having facings corresponding to the various cross-sectional shapes of the extruded members to be stretched, may run to a considerable amount in View of the necessity for accurately fitting the jaw facings to the cross-sectional shape of the extruded members. The cross grooving of the facings becomes a considerable problem.

The present invention contemplates a method of making the jaws, which reduces the expense thereof very considerably, and at the same time provides greater accuracy of conformity of the jaw gripping surfaces to the cross-sectional shape of the extruded member, than is possible under old methods. Another object is to provide a method whereby the major portion of a set of worn jaws may be salvaged and incorporated into a new set of jaws.

The invention further contemplates the provision of improved and novel jaw members formed in accordance with my improved method.

In the drawings, like reference characters designate similar parts in the several views.

Fig. l is a perspective exploded view of a section of an extruded shape, with a set of jaw facings fitted thereto preparatory to molding into a set of jaws.

Fig. 2 is a perspective view illustrating the method of making a set of jaws in accordance with my invention.

Fig. 3 is a perspective view of a set of jaws that have been constructed in accordance with the invention. a

As an example of one manner in which the invention may be practiced, I have shown in the drawings a method of producing a set of three jaws for engaging a T-shaped extrusion. The first step in the process is to prepare a short section of such extrusion, which is indicated generally at I0 in Fig. l. The particular extruded shape shown by way of example includes :a main flange [2, a flange l4 parallel to the flange l2 but offset from the plane thereof, with a stepped portion [6 lying between the two flanges, and a transverse flange l8.

The second step in the process is to form a set of jaw facings 20, 2|, 22, 23, 24, 25 and 26, adapted to fit the respective faces of the portions l2, l4, l6 and I8. The facings 20-26 are each serrated on one side to provide teeth 28 for engaging the surfaces of the flanges l2, l4 and I8, and on the opposite side are provided with anchor beads 30, of dove-tail cross section. Since each of the facings is a simple flat plate, the machining of the serrations which produce the teeth 28, and the machining of the beads 36 are relatively simple and inexpensive operations.

In the next step of the operation, the facings Zfl26 respectively are secured in place against the respective faces of the extrusion section It]. A simple method of doing this is to bind the facings with wire loops 32 wrapped around each pair of opposed facings and the flange member embraced therebetween. Any other suitable means for temporarily securing the facings to the extrusion, may be employed.

In the next step of the process, the bundle comprising the extrusion section l0 and the facings attached thereto, is placed in the mold cavity 34 of a mold 36. The cavity 34 has three main faces 38, adapted to define, together with the extrusion and facing package, three spaces of the proper shape to form three jaw sections A,

B and C respectively. Each face 38 is provided with a central, vertical bead 40 adapted to form, in its respective jaw, an impression 42 for locating an attaching rib 44 which is later secured to the respective jaw as by means of screws 46.

The next step in the process is to pour molten metal '48 into the mold cavity 34, filling the spaces between the bundle of jaw facings and the sides of the mold to form a casting in which the facings 2626 are securely anchoredby the beads 38. The sides 38 of the mold cavity converge toward the bottom of the mold box-:36. Thisfacilitates removal of the castingfromthemold. -It also provides faces 50 on the jaws A, B and C which diverge in the direction of pull in the stretching machine, and whichare adapted to cooperate with similarly diverging faces in the chuck members of the stretching machine (not .shown) so as to produce a wedging action which tightens the jaws against the extrusion under the pull of the machine. The'fa-ces 50 take the load so that the ribs 44 are required to function'only as locators and means for securingthe jaws in the chuck when the load is removed --fromthe aws.

While the invention contemplates the use of any suitable casting material, I find that Kirksite metal is particularly adaptable to the purpose of the invention, and has the necessary strength to endure the heavy loads-to which the jaws are submitted in service.

The next step in the process, after the casting has been removed from the mold, is to 'sawias at 52, 513 and 56) through the corners of the'casting to the extremities of the three flanges l2, l4 and I8 of the extrusion'section, thusseparating the casting into the three separate jaws A, B and C. Surfaces of the' jaws which have been formed by direct contact of the molten metal with the extrusion section II] (as at 58) are then undercut so as to avoid interference with full engagement of the extrusion surfaces by the jaw teeth 28. The protruding portions of the loops 32 are likewise machined oif, leaving the side portions of the loops'imbedded in the jaws. and the ribs 44 are then attached. The jaws. arethen ready to be installed in the stretching machine chuck.

rated hardened jaw facings, each facing having a contour complementary to and adapted to engage acorresponding portion of said workpiece wherebyall surfaces of said workpiece are engaged-by-saidfacings, the opposite side of each jawifacingbeing provided with a, plurality of anchor beads of dovetail cross section; and body portions of relatively soft cast material engagingsaidopposite sides and cooperating with said anchor beads to=--ho1d said jaw facings thereto, said body portions being--provided-with tapered sides remote from said jaw iacingspsaid tapered sides including rib portions projecting therefrom, said tapered sidesbeing in engagement with-said stretch formingmachine for-forcing said jaw facings into gripping engagement with said workpiece.

ELLIS W. COOPER.

- REFERENCES CITED The following references are ,of record-lathe file of .this patent:

UNITED STATES PATENTS Number Name Date 1,103,591 Kneass July 14,1914 1,647,387 Wood, Nov. 1, 1927 1,848,294 Howie Mar. 8, 1932 1,966,955 Crampton July 17, 1934 1,958,419 Cope May 15, 1934 1,989,996 'Mautsch Feb. 5, 1935 2,136,538 'Borwick Nov. 15, 1938 2,157,892 Godfriaux 'May 9,1939 2,218,503 Brooks et al Oct. .22, 1940 

